Accessory muscles and strabismus: cause or coincidence?

ABSTRACT

Anomalous extrinsic ocular muscles are rare findings but they should be suspected in cases of atypical and excessively restrictive strabismus, associated with vertical movements or retractions. They can also be seen as perioperative findings in characteristically normal deviations. We report two cases in which anomalous lateral rectus muscle was found during surgery. In case one, a 29-year-old man had a mild abduction limitation and esotropia of 35 prismatic diopters in his right eye. In the perioperative period, anomalous division of the RL fibers was observed, respecting their original insertion. We chose to suture the two portions of the muscle, uniting them posteriorly on the globe through a fixation point, in addition to recoiling the medial rectus muscle, resulting in postoperative orthotropy. In case two, in a patient with large-amplitude exotropia and positive forced duction test for adduction after the release of the lateral rectus muscle, 2mm posterior to it an accessory muscle structure was found, which was subsequently confirmed by the anatomopathological examination. Suturing it together with the original lateral rectus, in addition to the recoil of the muscle group, resulted in the permanence of the deviation. We alert to the surgical unpredictability related to such anomalous muscles, indicating their preoperative investigation to improve the procedure planning.

Keywords:
Strabismus; Accessory extrinsic ocular muscle; Supernumerary lateral rectus muscle; Anomalous lateral rectus muscle